Check-in: Physical and chemical changes

Identify signs of a chemical change occurring.

• Formation of a new gas, indicated by fizzing or a new odour

• A change in size, shape or state

• Two substances are mixed and can be separated again

• Production of light or sound

Identify whether the following statement is true or false. Possible signs of a chemical change include the disappearance of a solid and the formation of a new solid.

• True

• False

Determine what happens to chemical bonds during a chemical change.

• Chemical bonds are broken but no new bonds form

• All chemical bonds remain the same

• Some chemical bonds are broken and new bonds form

• New chemical bonds form but no chemical bonds are broken

Determine what happens to atoms during a chemical change.

• They turn into different atoms

• They are re-arranged to produce a new substance

• They change size and shape

• Nothing, they remain exactly as they were before the chemical change

Classify each of your friend's activities as either a physical or a chemical change.

Groups:

(a) Physical change

,

(b) Chemical change

• Boiling water in a kettle

• Stirring sugar into coffee

• Unfolding school uniform

• Dissolve instant coffee

• Toasting bread in a toaster

• Igniting gas flame on kitchen stove

• Frying some eggs

Your friend draws a model to show how the particles change when water is boiled. Analyse the model to identify the errors.

• A) The model shows the molecules moving further apart

• B) The model shows chemical bonds being broken and formed

• C) The model shows the same number of atoms before and after the change

• D) The model shows new substances being formed

You decide to help your friend by correcting their model.

Model the change that occurs when water is boiled by completing the diagram.

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